Whole body 3-methylhistidine production and proteinase activities in porcine muscle after protein-free feeding and realimentation

Abstract

Whole body 3-methylhistidine (3MH) production rates and proteinase activities in porcine skeletal muscles were studied during a protein-free feeding period and subsequent realimentation. Out of 54 castrated male pigs (35 kg on day 0), six pigs were slaughtered on day 0, and 48 were randomly divided between six dietary treatment groups. During the 14 day protein-free feeding period, three isocaloric diets were provided on a restricted basis: Control (C), protein-free, carbohydrate-rich (PF/CH) or protein-free, fat-rich (PF/FAT). On day 14, eight pigs per treatment group were slaughtered. During the seven day realimentation period, all remaining pigs received the control diet at a restricted level and this formed the other three treatment groups: C–C, PF/CH–C and PF/FAT–C. On day 21, these pigs were slaughtered. Measurement of the 3MH production rate was performed during the last three days of each period. Feeding either one of the PF diets stopped the growth rate and increased the 3MH production rate, whereas proteinase and inhibitor activities in skeletal muscles were not influenced. During realimentation, the growth rate and feed efficiency were higher for both PF–C treatments than for the C–C treatment only during the first three days. The 3MH production rate, as well as proteinase and inhibitor activities in muscles, were not different between treatment groups. These data suggest that compensatory growth occurred only during the first three days of the realimentation period, but pigs did not fully compensate.